Which of these is not the supreme organ of the OAU?

The option that is not the supreme organ of the OAU (Organization of African Unity) is "Appointment of staff." The supreme organ of the OAU is the Assembly of Heads of States and Government, which is made up of the heads of state or government of all member states and is responsible for making decisions on behalf of the organization. The Council of Ministers, which is made up of government ministers, also plays an important role in the OAU. The Administrative Secretary General is responsible for carrying out the day-to-day administrative work of the organization. "Appointment of staff" is not considered a supreme organ as it only refers to the process of hiring staff members, and is not responsible for making decisions on behalf of the organization.